linux-kernel - Re: [PATCH 6/6] perf: Add dcacheline sort

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Message-ID: <20140516133058.GN50500@redhat.com>
Date:	Fri, 16 May 2014 09:30:58 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	acme@...stprotocols.net, peterz@...radead.org,
	LKML <linux-kernel@...r.kernel.org>, namhyung@...il.com,
	eranian@...gle.com, Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH 6/6] perf: Add dcacheline sort

On Fri, May 16, 2014 at 01:47:57PM +0200, Jiri Olsa wrote:
> On Tue, May 13, 2014 at 12:48:17PM -0400, Don Zickus wrote:
> > In perf's 'mem-mode', one can get access to a whole bunch of details specific to a
> > particular sample instruction.  A bunch of those details relate to the data
> > address.
> > 
> > One interesting thing you can do with data addresses is to convert them into a unique
> > cacheline they belong too.  Organizing these data cachelines into similar groups and sorting
> > them can reveal cache contention.
> > 
> > This patch creates an alogorithm based on various sample details that can help group
> > entries together into data cachelines and allows 'perf report' to sort on it.
> > 
> > The algorithm relies on having proper mmap2 support in the kernel to help determine
> > if the memory map the data address belongs to is private to a pid or globally shared.
> > 
> > The alogortithm is as follows:
> > 
> > o group cpumodes together
> > o group entries with discovered maps together
> > o sort on major, minor, inode and inode generation numbers
> > o if userspace anon, then sort on pid
> > o sort on cachelines based on data addresses
> 
> needs some collumn width refresh or something..? ;-)

Not sure what you mean here.

> 
> # Overhead  Data Cacheline         
> # ........  .......................
> #
>      5.42%  [k] 0xffff8801ed832c40 
>      5.29%  [.] sys_errlist@@GLIBC_2.12+0xffffffcbf7dfc1ff                       
>      3.16%  [k] 0xffffffffff5690c0 
> 
> 
> also I've got again perf hanged up on opening device file
> 
> [jolsa@...va perf]$ sudo strace -p 29445
> Process 29445 attached
> open("/dev/snd/pcmC0D0p", O_RDONLY^CProcess 29445 detached
> 
> another one I recall was /dev/dri/card0 touched by X server
> 
> I guess those device files allow to mmap memory and we recorded
> memory access there.. we need check for this and do not try to
> open device files

Ok.  And that problem doesn't happen when my patch is not applied?  I am
not sure how this patch causes open device hangs.  I'll try to run this on
a box with X server running to duplicate.

Cheers,
Don
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